Heating, ventilating, and air-conditioning (HVAC) systems are commonly used to condition the air inside commercial and residential buildings. A typical HVAC system includes a furnace to supply heated air and an air-conditioner to supply cooled air to the building.
A system of ducts is typically used to route the heated or cooled air from the furnace or air-conditioner to various points within the building. For example, supply ducts can be run from an air-conditioner to one or more rooms in a building to provide cooled air to the rooms. In larger buildings, the ducts typically terminate in the space above a false ceiling, and a diffuser assembly is positioned within the false ceiling to deliver the conditioned air from the duct into the room of the structure. In addition, return ducts can be used to return air from the rooms to the air-conditioner or furnace for cooling or heating.
Damper assemblies are commonly used to control air flow through HVAC ducts. For example, a damper assembly can be used to restrict air flowing through a duct until the HVAC system determines that conditioned air needs to be provided to a room within the structure. The HVAC system can then, for example, turn on the air-conditioner blower and open the damper assembly to allow air to be forced through the duct and diffuser assembly into the room.
In large structures such as office buildings, the building can be divided into a series of zones so that conditioned air is only provided to a specific zone as needed. For example, each zone can include its own series of ducts, and damper assemblies can be positioned at a source of each series of ducts to open and close as necessary to deliver conditioned air to one or more of the ducts. In this manner, separate zones can be conditioned separately as desired.
While existing HVAC systems effectively provide conditioned air throughout a structure, such systems can be expensive to build and maintain. For example, initially duct work must be run from the HVAC system source (e.g., furnace or air-conditioner) to each separate point at which conditioned air is to be provided. Further, depending on how each “zone” within a structure is configured, it may be difficult to provide desired conditioning to a specific area of a building. For example, if the zones are too large in size, it may be difficult to provide the correct mixture of conditioned air for a given zone. In addition, if the rooms within a building are reconfigured after the HVAC system has been installed, it may be necessary to reroute existing duct work to provide a desired level of conditioning for the new configuration of rooms.
To overcome the problems associated with conventional HVAC systems, a so-called “duct-less” HVAC system has been developed. FIG. 1 schematically shows an example of this type of system 100. The system 100 includes an air supply plenum 120, an air return plenum 130, and a conventional air conditioning unit 110. The air supply plenum 120 is positioned above a floor space 159 desired to be cooled, and is separated from the floor space 159 by a barrier such as a suspended ceiling 172. The air return plenum 130 is positioned above the air supply plenum 120 and is separated from the air supply plenum 120 by a barrier layer 174. Air return conduits 125 pass through the air supply plenum 120 to provide fluid communication between the conditioned floor space 159 and the return plenum 130. The air conditioner 110 provides conditioned air to the air supply plenum 120 via air supply conduits 115 that pass through the return plenum 130.
The air supply plenum 120 is adapted to provide conditioned air to multiple zones 160A, 160B of the floor space 159. A separate damper or dampers 150A, 150B are provided for each of the different zones 160A, 160B. Zone 160A is cooled by opening damper 150A such that cool air flows from the air supply plenum 120 into the zone 160A. Similarly, to cool the zone 160B, the damper 150B is opened thereby allowing cool air from the air supply plenum 120 to flow into the zone 160B.
While the floor space 159 is shown divided into two regions 160A, 160B, it will be appreciated that in normal applications the given floor space may have a much larger number of zones. For example, in a given floor space of a building, each room of the building may be designated as a different zone thereby allowing the temperature of each room to be independently controlled. Also, while FIG. 1 shows a single floor space, in multi-floor buildings, the return and supply plenums can be positioned between the floors of the building.
In the system of FIG. 1, the air temperature and air pressure within the air supply plenum 120 are maintained at selected constant values. The supply plenum 120 preferably overlies the entire floor space of the building, and provides conditioned air to all of the zones of the floor space. Therefore, separate lines of ductwork are not required to be installed for each zone. This reduction in ductwork assists in reducing original construction costs and also reduces costs associated with reconfiguring a given floor plan.